Display Device

ABSTRACT

A display device includes a first substrate including a circuit portion and a transmission portion, a first organic light emitting diode disposed over one surface of the first substrate and overlapping with the circuit portion, a second organic light emitting diode disposed over the other surface of the first substrate and overlapping with the transmission portion, and a second substrate facing one surface of the first substrate, in which the first organic light emitting diode and the second organic light emitting diode emit light to the second substrate.

This application claims the priority benefit of Republic of Korea PatentApplication No. 10-2018-0166706 filed on Dec. 20, 2018, which isincorporated herein by reference for all purposes as if fully set forthherein.

BACKGROUND Field

The present disclosure relates to a display device, and moreparticularly, to a display device capable of improving an aperture ratioand a transmittance and reducing manufacturing cost.

Related Art

With the development of information society, the demand for displaydevices for displaying images is increasing in various forms. Thedisplay field has rapidly changed to a flat panel display device (FPD)which is thin and light and has a large area instead of a cathode raytube (CRT) having a large volume. The FPD includes a liquid crystaldisplay device (LCD), a plasma display panel (PDP), an organic lightemitting display device (OLED), and an electrophoretic display device(ED).

Among them, the OLED is a self-emission device of self-emitting light,which has an advantage of high response rate and high luminousefficiency, brightness, and viewing angle. Particularly, the OLED may beformed even on a flexible substrate, can be driven at a lower voltagethan a plasma display panel (PDP) or an inorganic electroluminescence(EL) display, and has an advantage of being relatively low in powerconsumption and excellent in color.

Recently, a transparent display device capable of being viewed throughthe rear surface from the front surface of the display device has beendeveloped. For example, a transparent organic light emitting displaydevice includes a sub-pixel that emits light and a transmission portionthrough which external light is transmitted, thereby realizing atransparent display device. There is a problem in that it is difficultto increase aperture ratios of the sub-pixel and the transmissionportion due to a tradeoff relationship in which the transmission portionbecomes smaller when the sub-pixel becomes larger, and the sub-pixelbecomes smaller when the transmission portion becomes larger.

SUMMARY

The present disclosure provides a display device capable of increasingbrightness and a lifetime, decreasing a haze, and improving color purityby increasing a light emitting portion.

The present disclosure provides a display device comprising a firstsubstrate including a circuit portion and a transmission portion, afirst organic light emitting diode disposed over one surface of thefirst substrate and overlapping with the circuit portion, a secondorganic light emitting diode disposed over the other surface of thefirst substrate and overlapping with the transmission portion, and asecond substrate facing one surface of the first substrate in which thefirst organic light emitting diode and the second organic light emittingdiode emit light to the second substrate.

The first organic light emitting diode may include a first drivingtransistor and the second organic light emitting diode may include asecond driving transistor.

The first driving transistor and the second driving transistor mayoverlap with each other with the second substrate interposedtherebetween.

The first organic light emitting diode may include a first lowerelectrode connected to the first driving transistor, a first organiclayer disposed on the first lower electrode, and a first upper electrodedisposed on the first organic layer, and the second organic lightemitting diode may include a second lower electrode connected to thesecond driving transistor, a second organic layer disposed on the secondlower electrode, and a second upper electrode disposed on the secondorganic layer.

The first lower electrode may be a reflection electrode and the secondlower electrode may be a transmission electrode.

The first lower electrode may overlap with the circuit portion and thesecond lower electrode may overlap with the transmission portion.

The first organic light emitting diode may emit at least two light ofred, green, and blue and the second organic light emitting diode mayemit one remaining light of red, green, and blue except for the lightemitted from the first organic light emitting diode.

The second organic light emitting diode may emit a single color oflight.

The first organic light emitting diode may further include a first banklayer for partitioning the first lower electrode and the second organiclight emitting diode may further include a second bank layer forpartitioning the second lower electrode.

The display device may further comprise a black matrix disposed on onesurface of the second substrate facing the first substrate, in which thefirst bank layer may have a width larger than the width of the blackmatrix and the second bank layer may have a width equal to or smallerthan the width of the black matrix.

The display device may further comprise a first pad portion disposedover one surface of the first substrate, a first printed circuit boardconnected to the first pad portion through a first chip-on film, asecond pad portion disposed over the other surface of the firstsubstrate, and a second printed circuit board connected to the secondpad portion through a second chip-on film, in which the first printedcircuit board and the second printed circuit board may overlap with eachother.

The display device may further comprise a first pad portion disposedover one surface of the first substrate, a first printed circuit boardconnected to the first pad portion through a first chip-on film, asecond pad portion disposed over the other surface of the firstsubstrate, and a second printed circuit board connected to the secondpad portion through a second chip-on film, in which the first printedcircuit board and the second printed circuit board may not overlap witheach other.

Embodiments also relate to a display device including a plurality ofsub-pixels. Each sub-pixel may include at least a part of a firstsubstrate. The part of the first substrate may include a circuit portionand a transmission portion adjacent the circuit portion. Thetransmission portion is configured to transmit light. Each sub-pixel mayalso include a first light emitting element disposed over one surface ofthe first substrate in the circuit portion, a first driving transistoron the one surface of the first substrate in the circuit portion, thefirst driving transistor electrically connected to the first lightemitting element, and a second light emitting element disposed overanother surface of the first substrate in the transmission portion.

Embodiments also relate to a display device including a plurality ofsub-pixels. Each sub-pixel may include at least a part of a firstsubstrate. The part of the first substrate may include anon-transmission portion and a transmission portion adjacent thenon-transparent portion. Each sub-pixel may also include a first lightemitting element disposed on one surface of the first substrate in thenon-transmission portion, and a second light emitting element disposedon another surface of the first substrate in the transmission portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain the principles of thedisclosure. In the drawings:

FIG. 1 is a schematic block diagram of an organic light emitting displaydevice, according to an embodiment of the present disclosure.

FIG. 2 is a schematic circuit configuration diagram of a sub-pixel,according to an embodiment of the present disclosure.

FIG. 3 is a diagram illustrating a detailed circuit configuration of asub-pixel, according to an embodiment of the present disclosure.

FIG. 4 is a plan view schematically illustrating a layout of sub-pixelsof the organic light emitting display, according to an embodiment of thepresent disclosure.

FIG. 5 is a cross-sectional view of a sub-pixel according to ComparativeExample of the present disclosure.

FIG. 6 is an example graph illustrating an aperture ratio of atransmission portion according to PPI.

FIG. 7 is an example graph illustrating an aperture ratio of a lightemitting portion according to an aperture ratio of the transmissionportion.

FIG. 8 is an example graph illustrating a relationship between alifetime and brightness according to a current density of an element.

FIG. 9 is a plan view illustrating an organic light emitting displaydevice according to an exemplary embodiment of the present disclosure.

FIG. 10 is a plan view illustrating an organic light emitting displaydevice according to another exemplary embodiment of the presentdisclosure.

FIG. 11 is a diagram schematically illustrating a sub-pixel array of theorganic light emitting display device according to the exemplaryembodiment of the present disclosure.

FIG. 12 is a diagram illustrating a front surface of the sub-pixel arrayof FIG. 11, according to an embodiment of the present disclosure.

FIG. 13 is a diagram illustrating a rear surface of the sub-pixel arrayof FIG. 11, according to an embodiment of the present disclosure.

FIG. 14 is a cross-sectional view illustrating a sub-pixel of theorganic light emitting display device according to the exemplaryembodiment of the present disclosure.

FIG. 15 is a cross-sectional view schematically illustrating an organiclight emitting display device according to Comparative Example.

FIG. 16 is a cross-sectional view schematically illustrating an organiclight emitting display device according to an Embodiment.

FIG. 17 is a table illustrating a haze and color purity of transmissionportions according to Comparative Example and Embodiment.

FIGS. 18 to 21 are cross-sectional views illustrating a manufacturingmethod of an organic light emitting display device according to anexemplary embodiment of the present disclosure by each process.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the attached drawings. Throughoutthe specification, like reference numerals denote substantially likecomponents. In describing the present disclosure, a detailed descriptionof known functions or configurations related to the present disclosurewill be omitted when it is deemed that they may unnecessarily obscurethe subject matter of the present invention. In addition, the componentnames used in the following description may be selected in considerationof easiness of specification, and may be different from the parts namesof actual products.

A display device according to the present disclosure is a display devicein which a display element is formed on a glass substrate or a flexiblesubstrate. As an example of the display device, an organic lightemitting display device, a liquid crystal display device, anelectrophoretic display device, or the like can be used, but in thepresent disclosure, the organic light emitting display device will bedescribed as an example. The organic light emitting display deviceincludes an organic layer formed of an organic material between a firstelectrode which is an anode and a second electrode which is a cathode.Accordingly, the organic light emitting display device is aself-emission display device in which holes supplied from the firstelectrode and electrons supplied from the second electrode are combinedin the organic layer to form excitons, which are hole-electron pairs,and light is emitted by energy generated when the excitons return to aground state.

The display device according to the present disclosure is an organiclight emitting display device having a top emission structure. Theorganic light emitting display device having the top emission structurehas a structure in which the light emitted from the light emitting layeris transmitted by passing through a transparent second electrode locatedat the upper side.

Hereinafter, exemplary embodiments of the present disclosure will bedescribed with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an organic light emitting displaydevice, according to an embodiment of the present disclosure, FIG. 2 isa schematic circuit configuration diagram of a sub-pixel, according toan embodiment of the present disclosure, and FIG. 3 is a diagramillustrating a detailed circuit configuration of a sub-pixel, accordingto an embodiment of the present disclosure.

As illustrated in FIG. 1, an organic light emitting display deviceincludes an image processor 110, a timing controller 120, a data driver130, a scan driver 140, and a display panel 150.

The image processor 110 outputs a data enable signal DE and the liketogether with a data signal DATA supplied from the outside. The imageprocessor 110 may output at least one of a vertical synchronizationsignal, a horizontal synchronization signal, and a clock signal inaddition to the data enable signal DE, but these signals will be notillustrated for convenience of description.

The timing controller 120 receives a data signal DATA from the imageprocessor 110 in addition to the data enable signal DE or a drivingsignal including the vertical synchronization signal, the horizontalsynchronization signal, and the clock signal. The timing controller 120outputs a gate timing control signal GDC for controlling an operationtiming of the scan driver 140 and a data timing control signal DDC forcontrolling an operation timing of the data driver 130 based on thedriving signal.

The data driver 130 samples and latches the data signal DATA suppliedfrom the timing controller 120 in response to the data timing controlsignal DDC supplied from the timing controller 120 and converts andoutputs the sampled and latched data signal into a gamma referencevoltage. The data driver 130 outputs the data signal DATA through datalines DL1 to DLn. The data driver 130 may be formed in the form of anintegrated circuit (IC).

The scan driver 140 outputs a scan signal in response to the gate timingcontrol signal GDC supplied from the timing controller 120. The scandriver 140 outputs a scan signal through gate lines GL1 to GLm. The scandriver 140 is formed in the form of an integrated circuit (IC) or formedon the display panel 150 in a gate-in-panel form.

The display panel 150 displays an image in response to the data signalDATA and the scan signal supplied from the data driver 130 and the scandriver 140. The display panel 150 includes sub-pixels SPs that operateto display the image.

The sub-pixels SPs include red sub-pixels, green sub-pixels, and bluesub-pixels or include white sub-pixels, red sub-pixels, greensub-pixels, and blue sub-pixels. The sub-pixels SPs may have one or moredifferent emission areas depending on emission characteristics.

As illustrated in FIG. 2, one sub-pixel includes a switching transistorSW, a driving transistor DR, a capacitor Cst, a compensation circuit CC,and an organic light emitting diode OLED.

The switching transistor SW operates switching so that the data signalsupplied through the data line DL in response to the scan signalsupplied through a first gate line GL1 is stored as a data voltage inthe capacitor Cst. The driving transistor DR operates so that a drivingcurrent flows between a power supply line EVDD (high potential voltage)and a cathode power supply line EVSS (low potential voltage) inaccordance with the data voltage stored in the capacitor Cst. Theorganic light emitting diode OLED operates to emit light in accordancewith the driving current generated by the driving transistor DR.

The compensation circuit CC is a circuit which is added in the sub-pixelto compensate a threshold voltage or the like of the driving transistorDR. The compensation circuit CC is constituted by one or moretransistors. The configuration of the compensation circuit CC variesgreatly according to an external compensation method, and an example ofthe compensation circuit CC will be described as follows.

As illustrated in FIG. 3, the compensation circuit CC includes a sensingtransistor ST and a sensing line VREF (or a reference line). The sensingtransistor ST is connected between a source electrode of the drivingtransistor DR and an anode electrode of the organic light emitting diodeOLED (hereinafter referred to as a sensing node). The sensing transistorST operates to supply an initialization voltage (or a sensing voltage)transmitted through the sensing line VREF to the sensing node of thedriving transistor DR or sense a voltage or current of the sensing nodeof the driving transistor DR or the sensing line VREF.

In the switching transistor SW, the source electrode or the drainelectrode is connected to the data line DL and the other one of thesource electrode and the drain electrode is connected to the gateelectrode of the driving transistor DR. In the driving transistor DR,the source electrode or the drain electrode is connected to the powersupply line EVDD and the other one of the source electrode and the drainelectrode is connected to a lower electrode which is an anode of theorganic light emitting diode OLED. In the capacitor Cst, a capacitorlower electrode is connected to the gate electrode of the drivingtransistor DR and a capacitor upper electrode is connected to the lowerelectrode of the organic light emitting diode OLED. In the organic lightemitting diode OLED, a lower electrode is connected to the other one ofthe source electrode and the drain electrode of the driving transistorDR and an upper electrode, which is a cathode electrode, is connected toa second power supply line EVSS. In the sensing transistor ST, a sourceelectrode or a drain electrode is connected to the sensing line VREF andthe other of the source electrode and the drain electrode is connectedto the lower electrode of the organic light emitting diode OLED which isthe sensing node and the other one of the source electrode and the drainelectrode of the driving transistor DR.

The operation time of the sensing transistor ST may be similar to or thesame as, or different from that of the switching transistor SW dependingon an external compensation algorithm (or a configuration of thecompensation circuit). For example, the gate electrode of the switchingtransistor SW may be connected to the first gate line GL1, and the gateelectrode of the sensing transistor ST may be connected to the secondgate line GL2. In this case, a scan signal Scan is transmitted to thefirst gate line GL1 and a sensing signal Sense is transmitted to thesecond gate line GL2. As another example, the first gate line GL1connected to the gate electrode of the switching transistor SW and thesecond gate line GL2 connected to the gate electrode of the sensingtransistor ST may be connected to each other to share in common.

The sensing line VREF may be connected to the data driver. In this case,the data driver may sense the sensing node of the sub-pixel during anon-display period of the image or an N frame (N is an integer of 1 ormore) in real time and generate a sensing result. On the other hand, theswitching transistor SW and the sensing transistor ST may be turned onat the same time. In this case, the sensing operation through thesensing line VREF and the data output operation for outputting the datasignal are separated (distinguished) from each other based on a timedivision system of the data driver.

In addition, an object to be compensated according to the sensing resultmay be a digital data signal, an analog data signal, a gamma, or thelike. A compensation circuit for generating a compensation signal (or acompensation voltage) based on the sensing result may be implemented inthe data driver, in the timing controller, or in a separate circuit.

In FIG. 3, the sub-pixel having a 3T(Transistor) 1C(Capacitor) structureincluding the switching transistor SW, the driving transistor DR, thecapacitor Cst, the organic light emitting diode OLED, and the sensingtransistor ST has been described as an example, but if the compensationcircuit CC is added, the sub-pixel may also be constituted by 3T2C,4T2C, 5T1C, 6T2C, and the like.

FIG. 4 is a plan view schematically illustrating a layout of sub-pixelsof the organic light emitting display according to an embodiment of thepresent disclosure, FIG. 5 is a cross-sectional view of a sub-pixelaccording to Comparative Example of the present disclosure, FIG. 6 is anexample graph illustrating an aperture ratio of a transmission portionaccording to PPI, FIG. 7 is an example graph illustrating an apertureratio of a light emitting portion according to an aperture ratio of thetransmission portion, and FIG. 8 is an example graph illustrating arelationship between a lifetime and brightness according to a currentdensity of an element.

Referring to FIG. 4, the organic light emitting display device of thepresent disclosure is a transparent display device that may be viewedthrough the rear surface from the front surface of the display device.The transparent organic light emitting display device includes first tofourth sub-pixels SPn1 to SPn4 for emitting light.

The first to fourth sub-pixels SPn1 to SPn4 are arranged with foursub-pixels in one row. The first and second sub-pixels SPn1 and SPn2constitute one first pixel PIX1 and the third and fourth sub-pixels SPn3and SPn4 constitute one second pixel PIX2. Each of the first to fourthsub-pixels SPn1 to SPn4 includes a light emitting portion EA having alight emitting element for emitting light and a circuit portion DA fordriving the light emitting element.

Each light emitting portion EA of each of the first to fourth sub-pixelsSPn1 to SPn4 emits red R, blue B and green G, respectively. For example,the first sub-pixel SPn1 may emit red R light, the second sub-pixel SPn2and the fourth sub-pixel SPn4 may emit green G light, and the thirdsub-pixel SPn3 may emit blue B light. However, the arrangement order ofthe sub-pixels may be variously changed depending on a light emittingmaterial, a light emitting area, a configuration (or structure) of thecompensation circuit, and the like.

Each of the first to fourth sub-pixels SPn1 to SPn4 has a transmissionportion for transmitting light to the upper side of the light emittingportion EA. Specifically, the first and second sub-pixels SPn1 and SPn2have a first transmission portion TA1, and the third and fourthsub-pixels SPn3 and SPn4 have a second transmission portion TA2.

Referring to FIG. 5, a cross-sectional structure of the sub-pixel willbe described.

Referring to FIG. 5, in an organic light emitting display deviceaccording to Comparative Example of the present disclosure, a bufferlayer 205 is disposed on a first substrate 200. The first substrate 200may be formed of glass, plastic, or metal. In the first substrate 200, afirst sub-pixel SPn1 and a first transmission portion TA1 are defined.The buffer layer 205 serves to protect a thin film transistor formed ina subsequent process from impurities such as alkali ions or the like,which are discharged from the first substrate 200. The buffer layer 205may be silicon oxide (SiOx), silicon nitride (SiNx), or a multilayerthereof.

A semiconductor layer 210 is disposed on the buffer layer 205. Thesemiconductor layer 210 may be formed of a silicon semiconductor or anoxide semiconductor. The silicon semiconductor may include amorphoussilicon or crystallized polycrystalline silicon. Here, thepolycrystalline silicon has high mobility (100 cm²/Vs or more), lowenergy consumption power, and excellent reliability to be applied to agate driver for a driving device and/or a multiplexer MUX or to adriving TFT in a pixel. On the other hand, since the oxide semiconductorhas a low off-current, the oxide semiconductor is suitable for aswitching TFT which maintains a short ON time and a long OFF time.Further, since the oxide semiconductor has the small off current and along voltage holding period of the pixel, the oxide semiconductor issuitable for a display device requiring low speed driving and/or lowpower consumption. In addition, the semiconductor layer 210 includes asource region and a drain region including p-type or n-type impurities,and includes a channel therebetween.

A gate insulating layer 215 is disposed on the semiconductor layer 210.The gate insulating layer 215 may be silicon oxide (SiOx), siliconnitride (SiNx), or a multilayer thereof. On the gate insulating layer215, the gate electrode 220 is disposed in a predetermined region of thesemiconductor layer 210, that is, a position corresponding to a channelwhen impurities are injected, and a capacitor lower electrode 225 isdisposed in a region spaced apart by a predetermined distance. The gateelectrode 220 and the capacitor lower electrode 225 may be formed of anyone selected from the group consisting of molybdenum (Mo), aluminum(Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium(Nd), and copper (Cu) or an alloy thereof. In addition, the gateelectrode 220 and the capacitor lower electrode 225 may be a multilayerformed of any one selected from the group consisting of molybdenum (Mo),aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni),neodymium (Nd), and copper (Cu) or an alloy thereof. For example, thegate electrode 220 and the capacitor lower electrode 225 may be a doublelayer of molybdenum/aluminum-neodymium or molybdenum/aluminum.

A first interlayer insulating layer 230 is formed on the gate electrode220 and the capacitor lower electrode 225 to insulate the gate electrode220 and the capacitor lower electrode 225 from each other. The firstinterlayer insulating layer 230 may be silicon oxide (SiOx), siliconnitride (SiNx), or a multilayer thereof. A capacitor upper electrode 235corresponding to the capacitor lower electrode 225 is disposed on thefirst interlayer insulating layer 230. The capacitor upper electrode 235may be formed of any one selected from the group consisting ofmolybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti),nickel (Ni), neodymium (Nd), and copper (Cu) or an alloy thereof.Accordingly, the capacitor lower electrode 225 and the capacitor upperelectrode 235 constitute the capacitor Cst.

A second interlayer insulating layer 240 is disposed on the firstinterlayer insulating layer 230 to insulate the capacitor upperelectrode 235. The second interlayer insulating layer 240 may be formedof the same material as the first interlayer insulating layer 230. Thegate insulating layer 215, the first interlayer insulating layer 230,and the second interlayer insulating layer 240 are formed with contactholes 237 exposing the semiconductor layer 210.

A drain electrode 250 and a source electrode 255 are disposed on thesecond interlayer insulating layer 240. The drain electrode 250 and thesource electrode 255 are connected to the semiconductor layer 210through the contact holes 237, respectively. The drain electrode 250 andthe source electrode 255 may be formed of a single layer or amultilayer, and when the drain electrode 250 and the source electrode255 are formed of the single layer, the drain electrode 250 and thesource electrode 255 may be formed of any one selected from the groupconsisting of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au),titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu) or an alloythereof. When the drain electrode 250 and the source electrode 255 areformed of the multilayer, the drain electrode 250 and the sourceelectrode 255 may be formed of a double layer ofmolybdenum/aluminum-neodymium, and a triple layer oftitanium/aluminum/titanium, molybdenum/aluminum/molybdenum ormolybdenum/aluminum-neodymium/molybdenum. Accordingly, a drivingtransistor DR including the semiconductor layer 210, the gate electrode220, the drain electrode 250 and the source electrode 255 isconstituted.

A passivation layer 260 is disposed on the first substrate 200 includingthe driving transistor DR. The passivation layer 260 may be a siliconoxide (SiOx) layer, a silicon nitride (SiNx) layer, or a multilayerthereof, as an insulating layer for protecting a lower element. Anovercoat layer 270 is disposed on the passivation layer 260. Theovercoat layer 270 may be a planarization layer for reducing a step ofthe lower structure and is formed of an organic material such aspolyimide, a benzocyclobutene series resin, or polyacrylate. A via hole274 is disposed in the overcoat layer 270 and the passivation layer 260to expose the source electrode 255 of the driving transistor DR.

An organic light emitting diode OLED is disposed on the overcoat layer270. More specifically, a lower electrode 280 is disposed on theovercoat layer 270 in which the via hole 274 is formed. The lowerelectrode 280 serves as a pixel electrode and is connected to the sourceelectrode 255 of the driving transistor DR through the via hole 274. Thelower electrode 280 as an anode may be formed of a transparentconductive material such as indium tin oxide (ITO), indium zinc oxide(IZO), or zinc oxide (ZnO). Since the present disclosure is an organiclight emitting display device having a top emission structure, the lowerelectrode 280 is a reflective electrode. Accordingly, the lowerelectrode 280 may further include a reflective layer. The reflectivelayer may be formed of aluminum (Al), copper (Cu), silver (Ag), nickel(Ni) or an alloy thereof, preferably a silver/palladium/copper (APC)alloy.

A bank layer 290 for partitioning the pixels is disposed on the overcoatlayer 270 on which the lower electrode 280 is formed. The bank layer 290is formed of an organic material such as polyimide, a benzocyclobuteneseries resin, or polyacrylate. In the bank layer 290, an opening 295 forexposing the lower electrode 280 is disposed.

An organic layer 310 is disposed on the first substrate 200 on which thebank layer 290 is formed. The organic layer 310 is formed to overlapwith at least the opening 295 of the bank layer 290 to be in contactwith the lower electrode 280. The organic layer 310 may include at leastone light emitting layer which emits light by combining electrons andholes and include at least one selected from a hole injection layer, ahole transport layer, an electron transport layer, and an electroninjection layer.

An upper electrode 320 is disposed on the organic layer 310. The upperelectrode 320 is disposed on a front surface of the first substrate 200and may be a cathode electrode. The upper electrode 320 may be formed ofmagnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or an alloythereof. The upper electrode 320 may be a transparent electrode capableof transmitting light.

A second substrate 340 facing the first substrate 200 is disposed. Thesecond substrate 340 may be a transparent glass substrate or a plasticsubstrate through which light may pass. A color filter 350 and a blackmatrix 360 are disposed on one surface of the second substrate 340, forexample, on a surface facing the first substrate 200. The color filter350 is provided to improve the color purity of the light emitted fromthe organic light emitting diode.

The organic light emitting display device configured as described aboveimplements images by emitting red, blue, and green light from the lightemitting portion of each sub-pixel, and may implement a transparentdisplay device by emitting light incident from the first substrate 200or the second substrate 340 from the transmission portion of eachsub-pixel.

Meanwhile, referring to FIG. 6, in the organic light emitting displaydevice, an aperture ratio of the transmission portion is graduallyreduced toward a high resolution (high pixels per inch (PPI)) due to anarea of the circuit portion for driving the light emitting portion ineach sub-pixel. Further, as illustrated in FIG. 7, when the apertureratio of the transmission portion is increased, the aperture ratio ofthe light emitting portion of each sub-pixel is reduced. When theaperture ratio of the light emitting portion is reduced, the currentdensity of the organic light emitting diode formed in each sub-pixel isincreased. Accordingly, as illustrated in FIG. 8, if the current densityof the organic light emitting diode formed in each sub-pixel isincreased, the lifetime of the organic light emitting diode is graduallyreduced. That is, FIG. 8 illustrates a result that the aperture ratioand the current density of the light emitting portion is inverselyproportional to each other and the luminance and lifetime are alsoinversely proportional to each other.

Hereinafter, there is disclosed a display device capable of improvingthe aperture ratios of the light emitting portion and the transmissionportion and improving the color purity thereof.

EMBODIMENTS

FIG. 9 is a plan view illustrating an organic light emitting displaydevice according to an exemplary embodiment of the present disclosure,FIG. 10 is a plan view illustrating an organic light emitting displaydevice according to another exemplary embodiment of the presentdisclosure, FIG. 11 is a diagram schematically illustrating a sub-pixelarray of the organic light emitting display device according to theexemplary embodiment of the present disclosure, FIG. 12 is a diagramillustrating a front surface of the sub-pixel array of FIG. 11,according to an embodiment of the present disclosure, and FIG. 13 is adiagram illustrating a rear surface of the sub-pixel array of FIG. 11,according to an embodiment of the present disclosure.

Referring to FIG. 9, an organic light emitting display device accordingto an exemplary embodiment of the present disclosure includes a displayarea AA and a non-display area NA on a first substrate 200.

A plurality of sub-pixels SP are arranged in the display area AA to emitR, G, and B light, thereby implementing full color. The display area AAincludes first organic light emitting diodes disposed on a front surfaceof the first substrate 200 and second organic light emitting diodesdisposed on a rear surface of the first substrate 200. The first organiclight emitting diode and the second organic light emitting diode will bedescribed below.

The non-display area NA includes a first pad portion PD1 and a secondpad portion PD2 disposed on one side of the first substrate 200. Thefirst pad portion PD1 is disposed on the front surface of the firstsubstrate 200 and the second pad portion PD2 is disposed on the rearsurface of the first substrate 200. First chip-on films COF1 for drivingthe first organic light emitting diode are attached to the first padportion PD1 and second chip-on films COF2 for driving the second organiclight emitting diode are attached to the second pad portion PD2. One endof the first chip-on film COF1 is connected to the first pad portion PD1and the other end of the first chip-on film COF1 is connected to a firstprinted circuit board PCB1. The first chip-on film COF1 transmitssignals such as a scan signal, a data signal, and a power supply signal,which are applied from the first printed circuit board PCB1, to thefirst organic light emitting diode of the display area AA. One end ofthe second chip-on film COF2 is connected to the second pad portion PD2and the other end of the second chip-on film COF2 is connected to asecond printed circuit board PCB2. The second chip-on film COF2transmits signals such as a scan signal, a data signal, and a powersupply signal, which are applied from the second printed circuit boardPCB2, to the second organic light emitting diode of the display area AA.The first pad portion PD1 and the second pad portion PD2 overlap witheach other with the first substrate 200 interposed therebetween and thefirst printed circuit board PCB1 and the second printed circuit boardPCB2 may also overlap with each other with the first substrate 200interposed therebetween.

In FIG. 9 described above, it is illustrated that the first and secondpad portions PD1 and PD2, the first and second chip-on films COF1 andCOF2, and the first and second printed circuit boards PCB1 and PCB2 areprovided on one side of the first substrate 200.

Meanwhile, referring to FIG. 10, in the organic light emitting displaydevice of the present disclosure, the first pad portion PD1, the firstchip-on film COF1, and the first printed circuit board PCB1 may bedisposed on a front surface of one side of the first substrate 200. Thefirst printed circuit board PCB1 is electrically connected to the firstpad portion PD1 through the first chip-on film COF1. The second padportion PD2, the second chip-on film COF2, and the second printedcircuit board PCB2 may be disposed on a rear surface of the other sideof the first substrate 200. The second printed circuit board PCB2 iselectrically connected to the second pad portion PD2 through the secondchip-on film COF2. The first pad portion PD1 and the second pad portionPD2 may not overlap with each other with the first substrate 200interposed therebetween and the first printed circuit board PCB1 and thesecond printed circuit board PCB2 may also not overlap with each otherwith the first substrate 200 interposed therebetween.

The arrangement of the sub-pixels of the organic light emitting displaydevice of the present disclosure described above will be described inmore detail below.

Referring to FIG. 11, an organic light emitting display device accordingto an exemplary embodiment of the present disclosure includes a firstsub-pixel SPn1 and a second sub-pixel SPn2.

The first sub-pixel SPn1 and the second sub-pixel SPn2 each function asone pixel. That is, the first sub-pixel SPn1 constitutes one first pixelPIX1 and the second sub-pixel SPn2 constitutes one second pixel PIX2.Each of the first sub-pixel SPn1 and the second sub-pixel SPn2 includesa light emitting portion EA having an organic light emitting diode foremitting light and a circuit portion DA for driving the organic lightemitting diode.

Each light emitting portion EA of the first sub-pixel SPn1 and thesecond sub-pixel SPn2 emits one light selected from red R, blue B andgreen G. For example, the first sub-pixel SPn1 may emit blue B light,and the second sub-pixel SPn2 may emit red R light. The first sub-pixelSPn1 and the second sub-pixel SPn2 include first and second transmissionportions TA1 and TA2 for transmitting light on the upper side of thelight emitting portion EA. Specifically, the first sub-pixel SPn1includes the first transmission portion TA1 and the second sub-pixelSPn2 includes the second transmission portion TA2.

Meanwhile, the organic light emitting display device of the presentdisclosure may emit light from the first transmission portion TA1 andthe second transmission portion TA2. Although FIG. 11 illustrates twosub-pixels for the sake of simplicity, in general, the display devicemay include a plurality of sub-pixels, and each sub-pixel may include acorresponding part of the first substrate with a circuit portion DA anda transmission portion TA. The transmission portion TA may be adjacentthe circuit portion DA, and may be configured to transmit light.

FIG. 12 is a diagram illustrating sub-pixels disposed on the frontsurface of the first substrate. Referring to FIG. 12, the front surfaceof the first substrate is configured to emit blue B light from the lightemitting portion EA of the first sub-pixel SPn1 and to transmit lightfrom the first transmission portion TA1. The front surface of the firstsubstrate is configured so that the light emitting portion EA of thesecond sub-pixel SPn2 emits red R light and the second transmissionportion TA2 transmits light. Therefore, external light is transmittedfrom the first and second transmission portions TA1 and TA2 to betransparent, and the light emitted from each light emitting portion EAmay be emitted.

FIG. 13 is a diagram illustrating sub-pixels disposed on the rearsurface of the first substrate. Referring to FIG. 13, the rear surfaceof the first substrate is configured so that green G light is emittedfrom the first transmission portion TA1 of the first sub-pixel SPn1 andgreen G light is emitted from the second transmission portion TA2 of thesecond sub-pixel SPn2. The light emitted from each of the transmissionportions TA1 and TA2 of the first and second sub-pixels SPn1 and SPn2 isemitted to the front surface of the first substrate.

In the first sub-pixel SPn1, a first organic light emitting diode isformed in the circuit portion DA and the light emitting portion EA onthe front surface of the first substrate to emit light to the frontsurface of the first substrate and transmit the light from the firsttransmission portion TA1. In addition, a second organic light emittingdiode is formed in the first transmission portion TA1 and the lightemitting portion EA on the rear surface of the first substrate and thelight emitted from the second organic light emitting diode may beemitted through the first transmission portion TA1.

Accordingly, the organic light emitting display device of the presentdisclosure may implement a transparent mode in which light is emittedthrough the light emitting portion EA in one sub-pixel andsimultaneously, external light is transmitted through the transmissionportion. Further, the organic light emitting display device of thepresent disclosure may implement a non-transparent mode in which lightis emitted through the light emitting portion EA in one sub-pixel andsimultaneously, light of a different color is transmitted through thetransmission portion.

Hereinafter, the organic light emitting display device of the presentdisclosure will be described in detail while describing thecross-sectional structure of the sub-pixel.

FIG. 14 is a cross-sectional view illustrating a sub-pixel of an organiclight emitting display device according to an exemplary embodiment ofthe present disclosure. In the following, the same reference numeralsare designated to the same components as those in FIG. 5 describedabove, and the description thereof will be simplified.

Referring to FIG. 14, the organic light emitting display deviceaccording to the exemplary embodiment of the present disclosure mayinclude a first driving transistor DR1 and a first organic lightemitting diode OLED1 electrically connected to the first drivingtransistor DR1 on a first substrate 200.

Specifically, a circuit portion DA, a light emitting portion EA, and afirst transmission portion TA1 are defined on a front surface of acorresponding part of the first substrate 200 for a pixel. A firstbuffer layer 205 is disposed on the first substrate 200 and a firstsemiconductor layer 210 is disposed on the first buffer layer 205. Afirst gate insulating layer 215 is disposed on the first semiconductorlayer 210 and a first gate electrode 220 is disposed on the first gateinsulating layer 215 at a position corresponding to a channel of thefirst semiconductor layer 210. A first capacitor lower electrode 225 isdisposed in a region spaced apart from the first gate electrode 220.

A first lower interlayer insulating layer 230 is disposed on the firstgate electrode 220 and the first capacitor lower electrode 225 and afirst capacitor upper electrode 235 is disposed on the first lowerinterlayer insulating layer 230. Accordingly, the first capacitor lowerelectrode 225 and the first capacitor upper electrode 235 constitute afirst capacitor Cst. A first upper interlayer insulating layer 240 isdisposed on the first lower interlayer insulating layer 230 to insulatethe first capacitor upper electrode 235. The first gate insulating layer215, the first lower interlayer insulating layer 230, and the firstupper interlayer insulating layer 240 are formed with first contactholes 237 exposing the first semiconductor layer 210.

A first drain electrode 250 and a first source electrode 255 aredisposed on the first upper interlayer insulating layer 240. The firstdrain electrode 250 and the first source electrode 255 are connected tothe first semiconductor layer 210 through the first contact holes 237,respectively. Accordingly, a first driving transistor DR1 including thefirst semiconductor layer 210, the first gate electrode 220, the firstdrain electrode 250 and the first source electrode 255 is constituted.

A first passivation layer 260 is disposed on the first substrate 200including the first driving transistor DR1 and a first overcoat layer270 is disposed on the first passivation layer 260. A first via hole 274is disposed in the first overcoat layer 270 and the first passivationlayer 260 to expose the first source electrode 255 of the first drivingtransistor DR1.

A first organic light emitting diode OLED1 is disposed on the firstovercoat layer 270. More specifically, a first lower electrode 280 isdisposed on the first overcoat layer 270 in which the first via hole 274is formed. The first lower electrode 280 serves as a pixel electrode andis connected to the first source electrode 255 of the first drivingtransistor DR1 through the first via hole 274. The first lower electrode280 as an anode may be formed of a transparent conductive material suchas indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO).Since the present invention is an organic light emitting display devicehaving a top emission structure, the first lower electrode 280 is areflective electrode. Accordingly, the first lower electrode 280 mayfurther include a reflective layer.

A first bank layer 290 for partitioning the pixels is disposed on thefirst overcoat layer 270 on which the first lower electrode 280 isformed. In the first bank layer 290, a first opening 295 for exposingthe first lower electrode 280 is disposed.

A first organic layer 310 is disposed on the first substrate 200 onwhich the first bank layer 290 is formed. The first organic layer 310overlaps with at least the first opening 295 of the first bank layer 290to be in contact with the first lower electrode 280. The first organiclayer 310 may include at least one light emitting layer which emitslight by combining electrons and holes and include at least one selectedfrom a hole injection layer, a hole transport layer, an electrontransport layer, and an electron injection layer.

A first upper electrode 320 is disposed on the first organic layer 310.The first upper electrode 320 is disposed on the front surface of thefirst substrate 200 and may be a cathode electrode. The first upperelectrode 320 may be formed of magnesium (Mg), calcium (Ca), aluminum(Al), silver (Ag), or an alloy thereof. The first upper electrode 320may be a transparent electrode capable of transmitting light.Accordingly, the first organic light emitting diode OLED1 including thefirst lower electrode 280, the first organic layer 310, and the firstupper electrode 320 is constituted.

The first driving transistor DR1 and the first organic light emittingdiode OLED1 described above are disposed in the circuit portion DA ofthe first substrate 200 and disposed in the light emitting portion EA orthe circuit portion DA of the first organic light emitting diode OLED1.The first driving transistor DR1 and the first organic light emittingdiode OLED1 may be disposed on one surface, for example, a front surfaceof the first substrate 200 in the circuit portion DA.

A second substrate 340 facing the first substrate 200 is disposed. Thesecond substrate 340 may be a transparent glass substrate or a plasticsubstrate through which light may pass. A color filter 350 and a blackmatrix 360 may be further disposed on one surface of the secondsubstrate 340, for example, on a surface facing the first substrate 200.The color filter 350 is provided to improve the color purity of thelight emitted from the organic light emitting diode. The black matrix360 is disposed in the circuit portion DA and is not disposed in thefirst transmission portion TA1 so as not to affect the transmission oflight. The color filter 350 and the black matrix 360 may be disposed inthe circuit portion DA of the first substrate 200. When the color filter350 is present, the first organic light emitting diode OLED1 may emitwhite light, but is not limited hereto.

The first driving transistor DR1 and the first organic light emittingdiode OLED1 are disposed in the circuit portion DA and the lightemitting portion EA emits the light. The first driving transistor DR1and the first organic light emitting diode OLED1 are not disposed in thefirst transmission portion TA1 so that the light is transmitted. Thefirst organic layer 310 and the upper electrode 320 of the first organiclight emitting diode OLED1 do not affect the transmission of light.Thus, the circuit portion DA may also be a non-transmission portion.

On the other hand, a second driving transistor DR2 and a second organiclight emitting diode OLED2 are disposed on the rear surface of the firstsubstrate 200.

Specifically, a second buffer layer 405 is disposed below the firstsubstrate 200 and a second semiconductor layer 410 is disposed below thesecond buffer layer 405. A second gate insulating layer 415 is disposedbelow the second semiconductor layer 410 and a second gate electrode 420is disposed below the second gate insulating layer 415 at a positioncorresponding to a channel of the second semiconductor layer 410. Asecond capacitor lower electrode 425 is disposed in a region spacedapart from the second gate electrode 420.

A second lower interlayer insulating layer 430 is disposed below thesecond gate electrode 420 and the second capacitor lower electrode 425and a second capacitor upper electrode 435 is disposed below the secondlower interlayer insulating layer 430. Accordingly, the second capacitorlower electrode 425 and the second capacitor upper electrode 435constitute a second capacitor Cst2. A second upper interlayer insulatinglayer 440 is disposed below the second lower interlayer insulating layer430 to insulate the second capacitor upper electrode 435. The secondgate insulating layer 415, the second lower interlayer insulating layer430, and the second upper interlayer insulating layer 440 are formedwith second contact holes 437 exposing the second semiconductor layer410.

A second drain electrode 450 and a second source electrode 455 aredisposed below the second upper interlayer insulating layer 440. Thesecond drain electrode 450 and the second source electrode 455 areconnected to the second semiconductor layer 410 through the secondcontact holes 437, respectively. Accordingly, a second drivingtransistor DR1 including the second semiconductor layer 410, the secondgate electrode 420, the second drain electrode 450 and the second sourceelectrode 455 is constituted.

A second passivation layer 460 is disposed below the first substrate 200including the second driving transistor DR2 and a second overcoat layer470 is disposed below the second passivation layer 460. A second viahole 474 is disposed in the second overcoat layer 470 and the secondpassivation layer 460 to expose the second source electrode 455 of thesecond driving transistor DR2.

The second organic light emitting diode OLED2 is disposed below thesecond overcoat layer 470. More specifically, a second lower electrode480 is disposed below the second overcoat layer 470 in which the secondvia hole 474 is formed. The second lower electrode 480 serves as a pixelelectrode and is electrically connected to the second source electrode455 of the second driving transistor DR2 through the second via hole474. The second lower electrode 480 as an anode may be formed of atransparent conductive material such as indium tin oxide (ITO), indiumzinc oxide (IZO), or zinc oxide (ZnO). Since the second organic lightemitting diode OLED2 has a bottom emission structure, the second lowerelectrode 480 may be a transparent electrode or a transmissiveelectrode. Further, the second lower electrode 480 is disposed in thefirst transmission portion TA1.

A second bank layer 490 for partitioning the pixels is disposed belowthe second overcoat layer 470 on which the second lower electrode 480 isformed. In the second bank layer 490, a second opening 495 for exposingthe second lower electrode 480 is disposed.

A second organic layer 510 is disposed below the first substrate 200 onwhich the second bank layer 490 is formed. The second organic layer 510may be formed on the entire surface of the first substrate 200 to be incontact with the second lower electrode 480 through the second opening495 of the second bank layer 490. The second organic layer 410 mayinclude at least one light emitting layer which emits light by combiningelectrons and holes and may include at least one selected from a holeinjection layer, a hole transport layer, an electron transport layer,and an electron injection layer.

A second upper electrode 520 is disposed below the second organic layer510. The second upper electrode 520 may be disposed on the entiresurface of the first substrate 200 and may be a cathode electrode. Thesecond upper electrode 520 may be formed of magnesium (Mg), calcium(Ca), aluminum (Al), silver (Ag), or an alloy thereof. The second upperelectrode 520 may be a reflective electrode capable of reflecting light.The second upper electrode 520 may also be a semi-transmissive andsemi-reflective electrode capable of reflecting and transmitting light.Accordingly, the second organic light emitting diode OLED2 including thesecond lower electrode 480, the second organic layer 510, and the secondupper electrode 520 is constituted.

A second encapsulation layer 530 is disposed below the second organiclight emitting diode OLED2. The second encapsulation layer 530 may beformed by an organic layer, an inorganic layer, or a single layer ormultilayer structure thereof to protect the second organic lightemitting diode OLED2 on the second encapsulation layer. A protectivefilm 540 is disposed below the second encapsulation layer 530 to protectthe upper components.

The second driving transistor DR2 is disposed in the circuit portion DAand the light emitting portion EA of the second organic light emittingdiode OLED2 is disposed in the first transmission portion TA1. Since thesecond organic light emitting diode OLED2 is a bottom emissionstructure, the light emitted from the second light emitting diode OLED2is emitted from the first transmission portion TA1 to be emitted to thesecond substrate 340 through the first substrate 200. Thus, the seconddriving transistor DR2 and the second organic light emitting diode OLED2may be disposed on another surface, for example, a rear surface of thefirst substrate 200 in the transmission portion TA. The second drivingtransistor DR2 may overlap with the first driving transistor DR1 in avertical direction. Also, since the first organic light emitting diodeOLED1 is disposed in the circuit portion DA, and the second organiclight emitting diode OLED2 is disposed in the transmission portion TA,the second light emitting diode OLED2 may not overlap with the firstorganic light emitting diode OLED1 in a vertical direction.

Therefore, in the organic light emitting display device according to theexemplary embodiment of the present disclosure described above, thelight emitted from the first organic light emitting diode OLED1 isemitted in a direction of the second substrate 340 and the light emittedfrom the second organic light emitting diode OLED2 may be emitted fromthe first transmitting portion TA1. In addition, although organic lightemitting diodes are described herein as an example, it is appreciatedthat the display device may include other types of light emittingelements other than organic light emitting diodes OLED1, OLED2. Forexample, the display device may include a first light emitting elementin place of the organic light emitting diode OLED1 and a second lightemitting element in place of the organic light emitting diode OLED2,such as a micro LED, LCD, and the like.

The organic light emitting display device of the present disclosure mayimplement a transparent mode and a non-transparent mode. Referring toFIG. 14 together with FIG. 12 described above, the first organic lightemitting diode OLED1 is disposed in the light emitting portion EA of thefirst sub-pixel SPn1 on the front surface of the first substrate. Thefirst organic light emitting diode OLED1 emits blue B light. On the rearsurface of the first substrate, the second organic light emitting diodeOLED2 is disposed in the first transmission portion TA1 of the firstsub-pixel SPn1. The second organic light emitting diode OLED2 transmitslight without emitting light. Therefore, the organic light emittingdisplay device may implement a transparent mode in which the lightemitting portion EA of the first sub-pixel SPn1 emits blue B light andthe first transmission portion TA1 transmits the light.

Referring to FIG. 14 together with FIG. 13, the first organic lightemitting diode OLED1 may emit blue B light and the second organic lightemitting diode OLED2 may emit green G light. Therefore, the organiclight emitting display device may implement a non-transparent mode inwhich the light emitting portion EA of the first sub-pixel SPn1 emitsblue B light and the first transmission portion TA1 transmits the greenG light.

In the organic light emitting display device of Comparative Exampleillustrated in FIGS. 4 and 5 described above, red, green, and bluecolors need to be formed in the organic light emitting diode formed ineach sub-pixel, respectively. Specifically, a light emitting materialthat emits red light is deposited on a red sub-pixel using a first finemetal mask (FMM), a light emitting material that emits green light isdeposited on a green sub-pixel using a second FMM, and a light emittingmaterial that emits blue light is deposited on a blue sub-pixel using athird FMM. That is, because of the three-light emitting materialdeposition processes using three FMMs, a dead zone is generated betweenthe light emitting portions of each sub-pixel due to a mask tolerance.Due to this dead zone, a width of the bank layer defining the lightemitting portion between sub-pixels needs to be increased.

On the other hand, in the organic light emitting display device ofEmbodiments illustrated in FIGS. 12 to 14 described above, since thesecond organic light emitting diode formed on the rear surface of thefirst substrate emits the same color, an open metal mask (OMM) may beused instead of the fine metal mask (FMM). The light emitting materialis deposited on the entire display portion, so that no dead zone isgenerated between the light emitting portions of sub-pixels of thesecond organic light emitting diode. Therefore, the width of the banklayer between sub-pixels formed on the rear surface of the firstsubstrate may be minimized enough to define the light emitting portion.In one instance, the first organic light emitting diodes OLED1 of theplurality of sub-pixels may be configured to emit at least two colors oflight from red, blue, and green light, and the second organic lightemitting diodes OLED2 of the plurality of sub-pixels may be configuredto emit one remaining color of light from the red, green, and blue lightthat does not correspond to the at least two colors emitted by the firstorganic light emitting diodes OLED1. In one instance, the first organiclight emitting diodes OLED1 may emit red and blue light, and the secondorganic light emitting diodes OLED2 may emit green light.

FIG. 15 is a cross-sectional view schematically illustrating an organiclight emitting display device according to Comparative Example, FIG. 16is a cross-sectional view schematically illustrating an organic lightemitting display device according to Embodiment, and FIG. 17 is a tableillustrating a haze and color purity of transmission portions accordingto Comparative Example and Embodiment.

Referring to FIG. 15, in an organic light emitting display deviceaccording to Comparative Example, a circuit portion DA, a first organiclight emitting diode OLED1, and a first bank layer 290 are disposed on afront surface of a first substrate 200. A black matrix 360 is disposedon a second substrate 340 in a region corresponding to the circuitportion DA. The first bank layer 290 is formed with a large width tocover the above-described dead zone. Accordingly, the first bank layer290 is formed to have a larger width than that of the black matrix 360.Accordingly, when external light is incident from the first substrate200 in a first transmission portion TA1, light is refracted andscattered while passing through the first bank layer 290 overlappingwith the first transmission portion TA1. Therefore, the haze of thetransmitted light is high and the color purity is low.

Referring to FIG. 16, in an organic light emitting display deviceaccording to Embodiment, a circuit portion DA, a second organic lightemitting diode OLED2, and a second bank layer 490 are disposed on a rearsurface of a first substrate 200. A black matrix 360 is disposed on asecond substrate 340 in a region corresponding to the circuit portionDA. The second bank layer 490 may be formed with a small width becausethere is no dead zone described above. Accordingly, the width of thesecond bank layer 490 may be equal to or smaller than that of the blackmatrix 360. Accordingly, when external light is incident from the firstsubstrate 200 in a first transmission portion TA1, as the light istransmitted to the first transmission portion TA1 as it is, the haze ofthe transmitted light is low and the color purity is improved.

As illustrated in FIG. 17, the organic light emitting display devicemanufactured according to Comparative Example exhibits a transmittanceof 47%, a haze of 6%, and color purity of 41%. The organic lightemitting display device manufactured according to Embodiment exhibits atransmittance of 59%, a haze of 2%, and color purity of 63%.Accordingly, in the organic light emitting display device according toEmbodiment of the present disclosure, it can be seen that thetransmittance, haze, and color purity characteristics of thetransmission portion may be improved by providing the second organiclight emitting diode on the rear surface of the first substrate.

Hereinafter, a manufacturing method of the organic light emittingdisplay device according to Embodiment of the present disclosuredescribed above will be described. Hereinafter, the materials for therespective components have been described above and will be omitted.

FIGS. 18 to 21 are cross-sectional views illustrating a manufacturingmethod of an organic light emitting display device according to anexemplary embodiment of the present disclosure by each process.

Referring to FIG. 18, a first buffer layer 205 is formed on a firstsubstrate 200. A first semiconductor layer 210 is formed on the firstbuffer layer 205 and a first gate insulating layer 215 is formed on thefirst semiconductor layer 210 to insulate the first semiconductor layer210. On the first gate insulating layer 215, a first gate electrode 220is formed in a region overlapping with the first semiconductor layer 210and simultaneously, a first capacitor lower electrode 225 is formed in aregion spaced apart from the first semiconductor layer 210. A firstlower interlayer insulating layer 230 is formed on the first capacitorlower electrode 225 and the first semiconductor layer 210. On the firstlower interlayer insulating film 230, a first capacitor upper electrode235 is formed in a region overlapping with the first capacitor lowerelectrode 225 to form a first capacitor Cst1. A first upper interlayerinsulating layer 240 is formed on the first substrate 200 on which thefirst capacitor Cst1 is formed.

Next, referring to FIG. 19, the first substrate 200 is inverted. Asecond buffer layer 405 is formed on one surface of the first substrate200 which is inverted. A second semiconductor layer 410 is formed on thesecond buffer layer 405 and a second gate insulating layer 415 is formedon the second semiconductor layer 410 to insulate the secondsemiconductor layer 410. On the second gate insulating layer 415, asecond gate electrode 420 is formed in a region overlapping with thesecond semiconductor layer 410 and simultaneously, a second capacitorlower electrode 425 is formed in a region spaced apart from the secondsemiconductor layer 410. A second lower interlayer insulating layer 430is formed on the second capacitor lower electrode 425 and the secondsemiconductor layer 410. On the second lower interlayer insulating film430, a second capacitor upper electrode 435 is formed in a regionoverlapping with the second capacitor lower electrode 425 to form asecond capacitor Cst2. A second upper interlayer insulating layer 440 isformed on the first substrate 200 on which the second capacitor Cst2 isformed.

The second gate insulating layer 415, the second lower interlayerinsulating layer 430, and the second upper interlayer insulating layer440 are formed with second contact holes 437 exposing the secondsemiconductor layer 410. A second drain electrode 450 and a secondsource electrode 455 are disposed on the second upper interlayerinsulating layer 440. The second drain electrode 450 and the secondsource electrode 455 are contacted and connected with the secondsemiconductor layer 410 through the second contact holes 437,respectively. Accordingly, a second driving transistor DR2 including thesecond semiconductor layer 410, the second gate electrode 420, thesecond drain electrode 450 and the second source electrode 455 ismanufactured.

A second passivation layer 460 is formed on the second drivingtransistor DR2 and a second overcoat layer 470 is formed on the secondpassivation layer 460. A second via hole 474 is formed in the secondpassivation layer 460 and the second overcoat layer 470 to expose thesecond source electrode 455. A second lower electrode 480 is formed onthe second overcoat layer 470. The second lower electrode 480 iscontacted and connected with the second source electrode 455 through thesecond via hole 474. Next, a second bank layer 490 is formed on thefirst substrate 200 on which the second lower electrode 480 is formed.In the second bank layer 490, a second opening 495 for exposing thesecond lower electrode 480 below the second bank layer is disposed. Aphotoresist PR serving as a protective film is coated on the second banklayer 490 to protect the first substrate 200 on which the second banklayer 490 is formed.

Next, referring to FIG. 20, the first substrate 200 is inverted again.The first gate insulating layer 215, the first lower interlayerinsulating layer 230, and the first upper interlayer insulating layer240 which are formed above are formed with first contact holes 237exposing the first semiconductor layer 210. A first drain electrode 250and a first source electrode 255 are disposed on the first upperinterlayer insulating layer 240. The first drain electrode 250 and thefirst source electrode 255 are contacted and connected with the firstsemiconductor layer 210 through the first contact holes 237,respectively. Accordingly, a first driving transistor DR1 including thefirst semiconductor layer 210, the first gate electrode 220, the firstdrain electrode 250 and the first source electrode 255 is manufactured.

A first passivation layer 260 is formed on the first driving transistorDR1 and a first overcoat layer 270 is formed on the first passivationlayer 260. A first via hole 274 is formed in the first passivation layer260 and the first overcoat layer 270 to expose the first sourceelectrode 255. A first lower electrode 280 is formed on the firstovercoat layer 270. The first lower electrode 280 is contacted andconnected with the first source electrode 255 through the first via hole274. Next, a first bank layer 290 is formed on the first substrate 200on which the first lower electrode 280 is formed. In the first banklayer 290, a first opening 295 for exposing the first lower electrode280 below the first bank layer is formed. A light emitting material isdeposited on the first bank layer 290 using a fine metal mask to form afirst organic layer 310. A first upper electrode 320 is formed on thefirst substrate 200 on which the first organic layer 310 is formed toform a first organic light emitting diode OLED1 including the firstlower electrode 280, the first organic layer 310 and the first upperelectrode 320. A first encapsulation layer 370 is formed on the firstsubstrate 200 including a first organic light emitting diode OLED1.

Next, a color filter 350 and a black matrix 360 are formed on onesurface of a second substrate 340 facing the first organic lightemitting diode OLED1. At this time, the color filter 350 is disposed tocorrespond to a light emitting portion EA of the first organic lightemitting diode OLED1. In addition, the black matrix 360 is disposed in acircuit portion DA excluding the light emitting portion EA and the firsttransmission portion TA1. Next, the first organic light emitting diodeOLED1 of the first substrate 200 and the color filter 350 of the secondsubstrate 340 are aligned so as to face each other and bonded to eachother.

Next, referring to FIG. 21, the first substrate 200 is inverted again.The photoresist PR formed on the second bank layer 490 is removed. Inaddition, a light emitting material is deposited on the first substrate200 on which the second bank layer 490 is formed by using an open metalmask to form a second organic layer 510. The first organic layer 310described above is deposited on each sub-pixel in a pattern shape usinga fine metal mask, but the second organic layer 510 is continuouslydeposited on the entire surface of the second bank layer 490. The secondorganic layer 510 is formed of a light emitting material that exhibitsthe same color in each sub-pixel. A second upper electrode 520 is formedon the second organic layer 510. Accordingly, a second organic lightemitting diode OLED2 including the second lower electrode 480, thesecond organic layer 510, and the second upper electrode 520 is formed.

A second encapsulation layer 530 is formed on the second substrate 200on which the second organic light emitting diode OLED2 is formed and aprotective film 540 is attached on the second encapsulation layer 530,thereby manufacturing the organic light emitting display deviceaccording to the exemplary embodiment.

In the organic light emitting display device of the present inventiondescribed above, the first driving transistor and the first organiclight emitting diode are formed on one surface of the first substrate byinverting the first substrate three times, and the second drivingtransistor and the second organic light emitting diode are formed on theother surface of the first substrate. The first organic layer of thefirst organic light emitting diode may be formed using the fine metalmask and the second organic layer of the second organic light emittingdiode may be formed using the open metal mask.

As described above, in the organic light emitting display deviceaccording to the exemplary embodiment of the present disclosure, thesecond organic light emitting diode is further formed on the rearsurface of the first substrate and the transmission portion also emitsthe light, thereby improving an aperture ratio. Further, in the organiclight emitting display device according to the exemplary embodiment ofthe present disclosure, the width of the bank layer formed on the secondorganic light emitting diode is equal to or smaller than that of theblack matrix, thereby improving transmittance, haze, and color puritycharacteristics in the transmission portion.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the scope of the principles of thisdisclosure. More particularly, various variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A display device comprising a plurality of sub-pixels, each sub-pixel comprising: at least a part of a first substrate, the part of the first substrate including a circuit portion and a transmission portion adjacent the circuit portion, the transmission portion configured to transmit light; a first light emitting element disposed over one surface of the first substrate in the circuit portion; a first driving transistor on the one surface of the first substrate in the circuit portion, the first driving transistor electrically connected to the first light emitting element; and a second light emitting element disposed over another surface of the first substrate in the transmission portion.
 2. The display device of claim 1, further comprising a second driving transistor on the another surface of the first substrate, the second driving transistor electrically connected to the second light emitting element.
 3. The display device of claim 2, wherein the second driving transistor is further disposed in the circuit portion, and wherein the first driving transistor and the second driving transistor overlap with each other with the first substrate interposed between.
 4. The display device of claim 1, wherein the first light emitting element and the second light emitting element do not overlap in a vertical direction.
 5. The display device of claim 1, wherein the first light emitting element includes a first lower electrode, disposed on the one surface of the first substrate in the circuit portion, a first organic layer disposed on the first lower electrode, and a first upper electrode disposed on the first organic layer, and wherein the second light emitting element includes a second lower electrode disposed on the another surface of the first substrate in the transmission portion, a second organic layer disposed on the second lower electrode, and a second upper electrode disposed on the second organic layer.
 6. The display device of claim 5, wherein the first lower electrode is a reflection electrode and the second lower electrode is a transmission electrode.
 7. The display device of claim 5, further comprising a first bank layer on at least a portion of the first lower electrode and a second bank layer on at least a portion of the second lower electrode.
 8. The display device of claim 7, further comprising: a second substrate disposed above the one surface of the first substrate; and a black matrix disposed on one surface of the second substrate facing the first substrate, wherein the first bank layer has a width larger than a width of the black matrix and the second bank layer has a width equal to or smaller than the width of the black matrix.
 9. The display device of claim 1, wherein the first light emitting elements of the plurality of sub-pixels is configured to emit at least two colors of light from red, green, and blue light, and the second light emitting elements of the plurality of sub-pixels is configured to emit one remaining color of light from red, green, and blue light that does not correspond to the at least two colors of light emitted from the first light emitting elements of the plurality of sub-pixels.
 10. The display device of claim 9, wherein the second light emitting elements of the plurality of sub-pixels emit a single color of light.
 11. The display device of claim 1, further comprising: a first pad portion disposed over a first side of the first substrate on the one surface of the first substrate; a first printed circuit board electrically connected to the first pad portion; a second pad portion disposed over the first side of the first substrate on the another surface of the first substrate; and a second printed circuit board electrically connected to the second pad portion.
 12. The display device of claim 1, further comprising: a first pad portion disposed over a first side of the first substrate on the one surface of the first substrate; a first printed circuit board electrically connected to the first pad portion; a second pad portion disposed over a second side of the first substrate opposite the first side on the another surface of the first substrate; and a second printed circuit board electrically connected to the second pad portion.
 13. A display device comprising a plurality of sub-pixels, each sub-pixel comprising: at least a part of a first substrate, the part of the first substrate including a non-transmission portion and a transmission portion adjacent the non-transparent portion; a first light emitting element disposed on one surface of the first substrate in the non-transmission portion; and a second light emitting element disposed on another surface of the first substrate in the transmission portion.
 14. The display device of claim 13, wherein the first light emitting element and the second light emitting element do not overlap in a vertical direction.
 15. The display device of claim 13, wherein the transmission portion of the first substrate is configured to transmit light.
 16. The display device of claim 13, further comprising a first driving transistor on the one surface of the first substrate in the non-transmission portion, the first driving transistor electrically connected to the first light emitting element.
 17. The display device of claim 16, further comprising a second driving transistor on the another surface of the first substrate in the non-transmission portion, the second driving transistor electrically connected to the second light emitting element.
 18. The display device of claim 17, wherein the first driving transistor and the second driving transistor overlap with each other with the first substrate interposed between.
 19. The display device of claim 13, wherein the first light emitting elements of the plurality of sub-pixels is configured to emit at least two colors of light from red, green, and blue light, and the second light emitting elements of the plurality of sub-pixels is configured to emit one remaining color of light from red, green, and blue light that does not correspond to the at least two colors of light emitted from the first light emitting elements of the plurality of sub-pixels.
 20. The display device of claim 19, wherein the second light emitting elements of the plurality of sub-pixels emit a single color of light. 